Conventionally, automotive automatic steering apparatuses are known in which it is determined that the steering wheel is operated by a driver and automatic steering is released if a detected value of steering torque on a steering shaft becomes greater than or equal to a predetermined value during automatic steering. However, the steering torque on the steering shaft may be increased not only due to operation of the steering wheel by the driver but also due to inertial force of the steering wheel. Consequently, if steering angular acceleration of the steering wheel is increased, there is a risk that automatic steering will be released erroneously due to the inertial force of the steering wheel.
Conventionally, in order to prevent the automatic steering being released erroneously, automotive automatic steering apparatuses have been proposed in which it is determine that a detected value of operating torque is increased by inertial force of a steering wheel instead of steering wheel operation by a driver and automatic steering is maintained without being released if a detected value of the steering angular acceleration is greater than a predetermined value even if a detected value of steering torque during automatic steering is greater than or equal to a predetermined value (see Patent Literature 1, for example).
Conventionally, in order to suppress vibration of a steering wheel during automatic steering that arises due to twisting of a torsion bar that is disposed on a steering shaft, automotive steering apparatuses have also been proposed in which a steering force that is determined based on torsion angle information for the torsion bar is applied to the steering shaft by a motor (see Patent Literature 2, for example).